Abstract:
A high early-strength admixture for precast hydraulic cement comprises a calcium salt and a copolymer having a carbon-containing backbone to which are attached cement-anchoring members, such as carboxyl groups, and to which are also attached oxyalkylene pendant groups by linkages selected from the group consisting of amide and imide members. The copolymers used are preferably formed by reacting an acrylic polymer with ammonia or an alkoxylated amine. The calcium salt, preferably calcium nitrite, and the copolymer can added simultaneously as one admixture, or separately. The invention relates also to methods for enhancing high early strength in concrete, cement, masonry, and mortar mixtures generally, and to precast concrete particularly, and also pertains to such hydraulic mixtures containing the calcium salt and copolymer.
Abstract:
The present invention relates to ahydraulic binder comprising a Portland clinker having a Blaine specific surface of 4000 to 5500 cm²/g, from 2.5 to 8 % of sulphate expressed by mass of SO 3 relative to the mass of clinker, from 1.5 to 10 % of calcium nitrite and/or calcium nitrate expressed as anhydrous mass relative to the mass of clinker and from 15 to 50 % of a mineral addition comprising calcium carbonate by mass relative to the total mass of binder.
Abstract:
A rapid setting cementitious composition useful for making cement boards employs an insoluble form of anhydrous calcium sulfate (anhydrite) to accelerate setting and to permit reducing the amount of high alumina cement usage.
Abstract:
The present invention relates to a hydraulic binder comprising: 25 to 60 % by mass of Portland clinker; 5 to 15 % by mass of a first mineral addition selected from: o mineral additions reacting with at least 400 mg/g of CaO according to the method at 90°C described in the NF P 18-513 Standard of December 30, 201 1, in Appendix A, and o latent hydraulic materials; a second mineral addition reacting with less than 400 mg/g of CaO according to the method described herein above; and either a third mineral addition with a base of calcium carbonate or calcium sulphate, or both; the hydraulic binder comprising at least 1 % by mass of reactive aluminium, which is to say that contributes to the development of strengths.
Abstract:
The present invention provides a composition and method involving the use of at least one cement dispersant mixed with a diphosphonic or triphosphonic acid or salt as a slump retention-enhancing agent that is chemically unreacted with the at least one cement dispersant, such that, when introduced into the aqueous environment of a cementitious mixture, slump retention-enhancing agent molecules move independently of cement dispersant molecules with respect to the cement particles.
Abstract:
A rapid setting cementitious composition useful for making cement boards employs an insoluble form of anhydrous calcium sulfate (anhydrite) to accelerate setting and to permit reducing the amount of high alumina cement usage. The rapid setting cementitious composition comprises as a reactive powder blend: (a) 35 to 90 wt% potland cement; (b) 0 to 55 wt% pozzolan; (c) 5 to 15 wt% high alumina cement and (d) 1 to 8 wt% insoluble calcium sulfate anhydrite.
Abstract:
A method for improving early strength of cements comprising introducing into a cement, preferably during the grinding thereof, (a) at least one water reducer comprising a polyoxyalkylene polymer; (b) a sugar; and (c) an alkali or alkaline earth metal chloride. In further exemplary embodiments, the polyoxyalkylene polymer preferably comprises a comb polymer having a backbone and pendant groups. Optionally, an amine may be included with the additives. Exemplary additives and cements and cementitious compositions, preferably blended cements, and more most preferably pozzolanic cements, comprising the additives are also disclosed.